Ancaster High Secondary School is warning parents and students about potential asbestos exposure.

The school, which is located on Jerseyville Rd., says the potential exposure happened Monday in a hallway outside the east wing cafeteria.

Asbestos in the ceiling was disturbed while a board contractor was investigating a concern with the HVAC system last Thursday evening.

The school says the work was done in a controlled environment but students and staff were able to use the area on Monday, after the contractor completed the work.

An outside environmental agency will conduct air sampling.

The hallway will remain closed until the results of the testing are known.